Psyche: Metal world mission targets 'iron volcanoes'

Up until now, the worlds we've visited with robotic spacecraft have been composed largely of rock, ice and gas.

But a Nasa mission due to launch in 2022 will visit an object thought to be made largely of metal.

16 Psyche is part of the asteroid belt - the sprawling mass of planetary leftovers that orbits the Sun between Mars and Jupiter.

About the size of the US state of Massachusetts, Psyche is the largest metallic asteroid known to science.

But how did this 200km-wide metal world come to be?

As planetary building blocks joined together to form bigger and bigger objects in the early Solar System, some became so large and hot that they melted. This process, called differentiation, allowed heavier constituents like iron to sink to the interior.

This resulted in some objects, like Earth, forming a rocky crust and mantle around an iron-nickel core. The core is the source of our planet's magnetic field, which protects the atmosphere from being stripped away by charged particles from space.

A widely held idea is that 16 Psyche is the exposed core of an extinct world, perhaps as large as Mars. This proto-planet must have been pounded by other objects, removing the rocky outer layers and leaving just the iron-nickel innards prone to the vacuum of space.

Prof Elkins-Tanton says the first task for the mission is to test whether Psyche is indeed a planetary core

Lindy Elkins-Tanton is principal investigator for Nasa's mission to Psyche. She said the first task for the mission after arriving in 2026 was to test the idea 16 Psyche was indeed a planetary core.

"So there are a bunch of different hypotheses over what it might be and how it might have formed."

After that, "we will go on to understand what its composition is", she explained. "Would it be compositionally similar to what we think the Earth's core is, or very different from that?"

The mission will seek to understand the asteroid's surface features, or topography. It's not known whether metallic objects like 16 Psyche are covered in a superficial layer of regolith - the dust, soil or bashed-up rock that's found at the surface of the Earth, the Moon, Mars and some asteroids. In addition, says Prof Elkins-Tanton, "we don't know what impacts into metal look like - they could look very different from impacts into rock or ice".

Scientists want to understand whether the metal asteroid produced a magnetic field as it cooled. If the asteroid froze from the inside out, similar to the cores of Earth and Mercury, there will be no record of one. But if Psyche froze from the outside in, as scientists hope, its crust may retain a magnetic memory, allowing the spacecraft to measure and map the asteroid's remnant magnetic field.

Outside-in cooling would also open the door to a process never before seen before on a celestial body: sulphur-iron volcanism.

"One of the things that happens when metal freezes is that it loses about 7% of its volume. So we have a crust that's solid and the inside is continuing to solidify, but it's losing its volume as it solidifies," said Prof Elkins-Tanton, from Arizona State University (ASU) in Tempe. "The crust has to crack and settle to accommodate the loss of volume during freezing."

A 3D-printed model of Psyche. This is one imagining of how the asteroid looks, but we have no idea what its surface is like

Studies of iron meteorites have shown that a sulphur-rich fluid sometimes forms inside the parent body. "We think that could get squeezed out through the cracks and form a kind of sulphur-iron volcanism on the cooling Psyche," said the mission's principal investigator.

She said the team was "super-excited about this", but explained that it was "completely hypothetical".

"Our very best and favourite model for Psyche is that it froze from the outside in, recording its [magnetic] field and that it would be covered in the now billions-of-years-old remnants of sulphur volcanoes," she explained.

The Psyche spacecraft will also test several important technological innovations. The engine uses inert gases - energised by electric power from the solar arrays - to provide gentle, non-stop thrust.

This solar-electric propulsion (SEP) system saves on fuel mass compared with conventional chemical propulsion, allowing the spacecraft to enter orbit around 16 Psyche and freeing up space for science instruments.

During flight, controllers will also test a communications system that uses laser light, rather than conventional radio waves.

The mission was formally chosen by Nasa in March 2018, along with a separate asteroid mission called Lucy. The Lucy mission will launch in 2021 to explore the Trojans, a group of asteroids that share Jupiter's orbit around the Sun.

Quelle: BBC

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Update: 9.04.2019

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Iron volcanoes may have erupted on metal asteroids

NASA's upcoming mission to the asteroid Psyche could look for signs of past eruptions, and evidence of 'ferrovolcanism' may also turn up in iron meteorites

Metallic asteroids are thought to have started out as blobs of molten iron floating in space. As if that's not strange enough, scientists now think that as the metal cooled and solidified, volcanoes spewing liquid iron could have erupted through a solid iron crust onto the surface of the asteroid.

This scenario emerged from an analysis by planetary scientists at UC Santa Cruz whose investigation was prompted in part by NASA's plans to launch a probe to Psyche, the largest metallic asteroid in the solar system. Francis Nimmo, professor of Earth and planetary sciences, said he was interested in the composition of metallic asteroids indicated by analyses of iron meteorites, so he had graduate student Jacob Abrahams work on some simple models of how the asteroids cooled and solidified.

"One day he turned to me and said, 'I think these things are going to erupt,'" Nimmo said. "I'd never thought about it before, but it makes sense because you have a buoyant liquid beneath a dense crust, so the liquid wants to come up to the top."

The researchers described their findings in a paper that has been accepted for publication in Geophysical Research Letters and is available online.

Metallic asteroids originated early in the history of the solar system when planets were beginning to form. A protoplanet or "planetesimal" involved in a catastrophic collision could be stripped of its rocky outer layers, exposing a molten, iron-rich core. In the cold of space, this blob of liquid metal would quickly begin to cool and solidify.

"In some cases it would crystallize from the center out and wouldn't have volcanism, but some would crystallize from the top down, so you'd get a solid sheet of metal on the surface with liquid metal underneath," Nimmo said.

As for what the iron volcanoes would look like, Abrahams said it depends on the composition of the melt. "If it's mostly pure iron, then you would have eruptions of low-viscosity surface flows spreading out in thin sheets, so nothing like the thick, viscous lava flows you see on Hawaii," he said. "At the other extreme, if there are light elements mixed in and gases that expand rapidly, you could have explosive volcanism that might leave pits in the surface."

NASA's Psyche mission is scheduled to launch in 2022 and reach the asteroid in 2026. Signs of past volcanism that researchers could look for include variations in the color or composition of material on the surface, and possibly features that look like volcanic vents. Large volcanic cones are probably unlikely, Abrahams said.

Unfortunately, because metallic asteroids would have solidified fairly quickly after their formation, there has been plenty of time (billions of years) for any surface features of volcanism to be degraded. "It's not clear what they might look like now," Abrahams said.

The best opportunity to find evidence of ferrovolcanism on metallic asteroids might actually come from studying iron meteorites already in collections on Earth, the researchers said.

"There are lots of these metallic meteorites, and now that we know what we're looking for, we might find evidence of volcanism in them," Nimmo said. "If material got erupted onto the surface, it would cool very fast, which would be reflected in the composition of the meteorite. And it might have holes in it left by escaping gas."

"It's not a shocking idea, but we'd just never thought about iron volcanism before, so it's something new and interesting to investigate," Abrahams said.

This research was supported in part by NASA.

Quelle: UC SANTA CRUZ

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Update: 12.06.2019

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NASA's Psyche Mission Has a Metal World in Its Sights

Designed to explore a metal asteroid that could be the heart of a planet, the Psyche mission is readying for a 2022 launch. After extensive review, NASA Headquarters in Washington has approved the mission to begin the final design and fabrication phase, otherwise known as Phase C. This is when the Psyche team finalizes the system design, develops detailed plans and procedures for the spacecraft and science mission, and completes both assembly and testing of the spacecraft and its subsystems.

"The Psyche team is not only elated that we have the go-ahead for Phase C, more importantly we are ready," said Principal Investigator Lindy Elkins-Tanton of Arizona State University in Tempe. "With the transition into this new mission phase, we are one big step closer to uncovering the secrets of Psyche, a giant mysterious metallic asteroid, and that means the world to us."

The mission still has three more phases to clear. Phase D, which will begin sometime in early 2021, includes final spacecraft assembly and testing, along with the August 2022 launch. Phase E, which begins soon after Psyche hits the vacuum of space, covers the mission's deep-space operations and science collection. Finally, Phase F occurs after the mission has completed its science operations; it includes both decommissioning the spacecraft and archiving engineering and science data.

The Psyche spacecraft will arrive at Asteroid Psyche on Jan. 31, 2026, after flying by Mars in 2023.

Asteroid Psyche is one of the most intriguing targets in the main asteroid belt. While most asteroids are rocky or icy bodies, scientists think Psyche is composed mostly of iron and nickel, similar to Earth's core. They wonder whether Psyche could be the nickel-iron heart, or exposed core, of an early planet maybe as large as Mars that lost its rocky outer layers through violent collisions billions of years ago. If so, it would provide a unique look into the solar system's distant past, when the kind of high-speed protoplanet encounters that created Earth and the other terrestrial planets were common.

The Psyche mission aims to understand the building blocks of planet formation by exploring firsthand a wholly new and uncharted type of world. Along with determining whether Psyche is the core of an early planet, the team wants to determine how old it is, whether it formed in similar ways to Earth's core and what its surface is like.

The spacecraft's instrument payload includes three science instruments. The mission's magnetometer is designed to detect and measure the remnant magnetic field of the asteroid. The multispectral imager will provide high-resolution images using filters to discriminate between Psyche's metallic and silicate constituents. Its gamma ray and neutron spectrometer will detect, measure and map Psyche's elemental composition. The mission also will test a sophisticated new laser communications technology, called Deep Space Optical Communications.

The Psyche mission is part of NASA's Discovery Program, a series of lower-cost, highly focused robotic space missions. Psyche Principal Investigator Lindy Elkins-Tanton is the director of ASU's School of Earth and Space Exploration. Other ASU researchers on the Psyche mission team include Jim Bell, deputy principal investigator and co-investigator; David Williams, co-investigator; and Catherine Bowman, co-investigator and student-collaborations lead.

NASA's Psyche Mission to Metal Asteroid Enters Final Design Phase

NASA’s Psyche mission is preparing to go someplace that no other planetary mission has been to before: a metal asteroid. Now, NASA Headquarters in Washington has approved the start of the final design and fabrication phase of the mission, known as Phase C.

Psyche is scheduled to launch in August 2022 from Kennedy Space Center in Florida and will investigate the asteroid 16 Psyche in the main asteroid belt between Mars and Jupiter, which is much richer in metals than most asteroids, and is thought to likely be the remnant core of a once larger planet.

In Phase C, the Psyche team will finalize the system design of the spacecraft, develop detailed plans and procedures and complete both assembly and testing of the spacecraft and its subsystems.

“The Psyche team is not only elated that we have the go-ahead for Phase C, more importantly we are ready,” said Principal Investigator Lindy Elkins-Tanton of Arizona State University in Tempe. “With the transition into this new mission phase, we are one big step closer to uncovering the secrets of Psyche, a giant mysterious metallic asteroid, and that means the world to us.”

The continuation on to Phase C is great news, but there are still three more phases to be completed. Phase D will begin sometime in early 2021, and includes final spacecraft assembly and testing, as well as the August 2022 launch. Phase E covers the mission’s deep-space operations and science data collection. Finally, Phase F occurs after the mission has completed its science operations, and includes both decommissioning the spacecraft and archiving the engineering and science data for later study.

It is exciting to see the progress of this mission, since no other spacecraft has visited this kind of an asteroid before. While most asteroids are rocky, 16 Psyche is composed of iron and nickel, very similar to Earth’s own core.

The Psyche spacecraft will use three science instruments to explore the asteroid: the magnetometer will detect and measure the remnant magnetic field of the asteroid, the multispectral imager will provide high-resolution images using filters to discriminate between Psyche’s metallic and silicate constituents and the gamma ray and neutron spectrometer will detect, measure and map Psyche’s elemental composition.

Radar images of 16 Psyche from Nov. 28 – Dec. 9, 2015, by the Arecibo Observatory. These are the best views we have so far of this enigmatic little world. Image Credit: Arecibo Observatory.

Also to be tested is a sophisticated new laser communications technology, called Deep Space Optical Communication (DSOC). This encodes data in photons rather than radio waves to communicate between a probe in deep space and Earth. Using light instead of radio allows the spacecraft to communicate more data in a given amount of time.

If 16 Psyche really is the remnant core of a former planet, that planet may have been as large as Mars, and its outer mantle and crust were probably ripped away by violent collisions with other asteroids and protoplanets as the planet was forming in the early Solar System. The metallic “heart” is all that remains now.

16 Psyche represents a unique exploration opportunity for planetary scientists. Being able to study this type of asteroid up close will help scientists determine how old it is and whether it formed in a similar manner to Earth’s core. Even if it isn’t a former planet’s core, it will still provide valuable information about the building blocks of planets in the early Solar System. And of course, we will get to see what it actually looks like. Right now, we only have low-resolution fuzzy photos and radar images, as well as shape models, to go by. But the Psyche spacecraft will see the asteroid in exquisite detail.

Psyche will arrive at the asteroid on Jan. 31, 2026 and will orbit it until at least 2027.

The asteroid was discovered in 1852 and was named after the nymph Psyche, who married Cupid but was put to death by Venus. At Cupid’s request, however, Jupiter made Psyche immortal.

A growing number of asteroids, and comets, have been visited by spacecraft from Earth, but they have all been rocky and/or icy bodies. This is the first time that a metallic asteroid will be studied up close. The findings will help scientists to better understand how our Solar System originated and evolved over billions of years.

The Psyche mission, led by Arizona State University, is part of NASA’s Discovery Program, a series of lower-cost, highly-focused robotic space missions. More information about Psyche is available on the mission website.

Qwelle:

Radar images of 16 Psyche from Nov. 28 – Dec. 9, 2015, by the Arecibo Observatory. These are the best views we have so far of this enigmatic little world. Image Credit: Arecibo Observatory.

Also to be tested is a sophisticated new laser communications technology, called Deep Space Optical Communication (DSOC). This encodes data in photons rather than radio waves to communicate between a probe in deep space and Earth. Using light instead of radio allows the spacecraft to communicate more data in a given amount of time.

If 16 Psyche really is the remnant core of a former planet, that planet may have been as large as Mars, and its outer mantle and crust were probably ripped away by violent collisions with other asteroids and protoplanets as the planet was forming in the early Solar System. The metallic “heart” is all that remains now.

16 Psyche represents a unique exploration opportunity for planetary scientists. Being able to study this type of asteroid up close will help scientists determine how old it is and whether it formed in a similar manner to Earth’s core. Even if it isn’t a former planet’s core, it will still provide valuable information about the building blocks of planets in the early Solar System. And of course, we will get to see what it actually looks like. Right now, we only have low-resolution fuzzy photos and radar images, as well as shape models, to go by. But the Psyche spacecraft will see the asteroid in exquisite detail.

Psyche will arrive at the asteroid on Jan. 31, 2026 and will orbit it until at least 2027.

The asteroid was discovered in 1852 and was named after the nymph Psyche, who married Cupid but was put to death by Venus. At Cupid’s request, however, Jupiter made Psyche immortal.

A growing number of asteroids, and comets, have been visited by spacecraft from Earth, but they have all been rocky and/or icy bodies. This is the first time that a metallic asteroid will be studied up close. The findings will help scientists to better understand how our Solar System originated and evolved over billions of years.

The Psyche mission, led by Arizona State University, is part of NASA’s Discovery Program, a series of lower-cost, highly-focused robotic space missions. More information about Psyche is available on the mission website.